One of the oldest lines in Georgia, the Southwestern Railroad was chartered to build a railroad from Macon through southwestern Georgia to the lower Chattahoochee River in 1845.  Construction, which began around 1848, proceeded slowly. By 1852, the rails had been laid from Macon only as far as the Flint River at Oglethorpe. The next year the line was extended to Americus, aided by a $75,000 investment by Americus citizens. In 1857, the Southwestern purchased the line between Americus and Albany then under construction by the Georgia and Florida Railroad and pushed it to completion. The latter company was consolidated into the Southwestern in late 1859.

At Fort Valley, a branch was built westward to meet the unfinished Muscogee Railroad, a 50-mile line begun in 1847 as a Columbus-to-Macon route. When the Muscogee faltered in 1853, the Southwestern stepped in to complete the connection to the Muscogee’s eastern end at Butler. The Muscogee was consolidated into the Southwestern in 1856.
At Smithville, about 12 miles south of Americus, the Southwestern built another branch that ran westward to Cuthbert. Three miles west of Cuthbert, the rails branched again with one line leading west to Eufaula and the other 19 miles southwest to Fort Gaines. Both segments were completed in 1860.
On June 24, 1869, the Southwestern was leased to the Central of Georgia. Under the Central lease the railroad continued to construct branch lines, adding Albany to Arlington in 1873, Fort Valley to Perry in 1875, Arlington to Blakely in 1881, and Blakely to Columbia in 1889.
In 1954, the Central acquired a majority of the Southwestern’s stock and made the railroad an integral part of its own system.